My husband is heading off to the high Sierras for a backpacking trip this month. Patrick has done this trip before and was freezing all night. "I bought a cold weather sleeping bag, but I have never been colder in my life," he reported upon returning. "Next time I'm going prepared." Well, next time is here, and he's still not prepared. Enter Eve. My first call was to Adventure 16 Gear & Clothing. "I was camping in the Sierras in a 15-degree bag at the end of June," said the salesman, "and my 15-degree worked fine. But there's a whole system involved with the sleeping bag. If he didn't have a proper rated sleeping bag, that can definitely be a problem. All bags are rated for being on top of a sleeping pad that has an insulating property. So you need a good insulated sleeping pad. We have the ProLite 3 pad by Thermarest ( $74.99 ), which is pretty much the lightest weight pad you can buy, but the ProLite 4 ( $94.99 ) offers a bit more insulation.

"So the sleeping pad is the first thing I would look at. Then find out what degree sleeping bag that was. And if it was an older bag, depending on the condition of the bag, they can lose a lot of their property as well. If they have been stuffed and crammed for a while, the down will break down. The synthetic bags usually break down after five years of stuffing and re-stuffing."

The salesman at REI Outdoor Gear offered some other possible reasons why Patrick was freezing. "There are a few things that would have negated the bag. A lot of times, if it's a 15-degree bag, that means you are kept alive at 15 degrees; that doesn't mean it's going to keep you comfortable at 15 degrees. Add 10 to 15 degrees onto what the bag is rated for, and that is where you would be comfortable. So with a 20-degree bag, you are going to be comfortable around 30 to 35 degrees."

He continued, "One of the main reasons why people return their bags, thinking they didn't work, is because they weren't sleeping on an insulation pad. A sleeping bag is all about insulation, but when you are lying on the bottom, you are crushing that insulation, so it's not actually insulating you from anything. Also, if the bag is too big for him, that can be a problem. The bigger the bag the more your body has to work to warm up that dead space. So something that fits real tight will insulate a lot better."

The salesman recommended the REI Mojave, a 15-degree down bag for $169 .

"The earth basically sucks all your body heat out of your body," offered the salesman at C & C Outdoor Store. "So if you have an air pocket between you and the earth, which is what the pad is, it creates a pressure barrier, so it literally makes an air pocket. It is the same thing as a rain fly on a tent. What keeps the moisture from coming through the fabric of the tent is that there is a pressure difference in the air pocket between the outside air and the inside of the tent.

"Also, they are under so much pressure to make sleeping bags lighter and lighter weight. A lot of manufacturers are taking some of the fill off of the bottom of the bag because they assume you are going to crush it anyway and that takes weight out of the overall bag, making it more competitive in the market. But that also makes the problem worse."

The salesman laid out the differences between sleeping-bag materials. "Synthetic bags typically are cheaper priced than down bags. And there are different qualities of each. Down bags are real goose-down feathers, and they tend to insulate a lot better per pound. Down bags are lighter weight because the feathers are lightweight. If I had a 20-degree goose-down bag and a 20-degree synthetic fiber bag, I would probably be warmer in the goose down because it traps heat better, the feathers insulate. There are higher quality goose-down feathers versus lower quality goose-down feathers. Smaller, finer feathers, when they are all on top of each other, leave less air pockets inside the actual bag, inside the guts, and that means that less heat is going to escape, so they insulate better. You can still stay well under $200 for a nice quality down bag, but you can easily get under $80 for a 30-degree synthetic bag. It just may be a little heavier. Synthetic doesn't compress as much as down, so it's going to be bigger. Down compresses really small. If you know you are not going to be in a rainstorm, I would go with a down bag. And there are better bags to choose from, though in a bit more expensive range."

Asked to recommend a good deal on a bag that will keep Patrick warm, he responded, "I have 20-degree down Moonstone bags still in stock, the most popular bag they made [before the company was bought out by Columbia] retailed for $260, and I have those on sale for $150 . I have a 25-degree synthetic bag by them for $70 . It will be about a half-pound heavier.

"I have Lafuma bags, which are probably my smallest and lightest, at 1 pound, 12 ounces, and they are $125 for a 30-degree down bag.

"Big Agnes is a very popular brand this year, and they have 15-degree bags in the $180 price range. Their bags have an extra feature, a sleeve underneath where you can slide your sleeping pad into the bag and keep it anchored to it."

Finally, he suggested that Patrick could have been cold due to dehydration or too little body fat. Well, I know the latter couldn't have been the problem.